1. Field of the Invention
The present invention relates to a light deflecting apparatus, and more particularly, to a light deflecting apparatus having an improved bearing arrangement.
2. Description of the Related Art
A scan-type optical system incorporated in a laser printer or some other apparatus of this kind is provided with a light deflecting apparatus for deflecting light beams. This light deflecting apparatus comprises a motor and a rotating polygon mirror. In this apparatus, an incident light beam is reflected at an equiangular speed, and the polygon mirror is used for deflection scanning. The rotating polygon mirror has a plurality of reflecting surfaces (e.g., four or eight surfaces), and is fixed to the rotating shaft of the motor. It scans information to be recorded on a photoreceptor. In doing this, the polygon mirror rotates at a speed (e.g., 16,000 rpm) much higher than the speed (peripheral speed) at which the photoreceptor rotates in its auxiliary scanning direction. Accordingly, the rotating shaft of the motor should be supported by means of bearings to absorb load attributable to its rotation. When using dynamic-pressure air bearings for this purpose, the manufacture of the bearings requires very high machining accuracy. Although the dynamic-pressure air bearings can stand prolonged continuous use relatively well, extremely high accuracy is required for the machining of the gap between the motor shaft and the bearings. When using bearings (e.g., ball bearings, roller bearings, etc.) with rolling bodies in the light deflecting apparatus, conventional ones, whose maximum allowable rotational frequency is low, sometimes cannot function as satisfactory bearings. In other words, the maximum allowable rotational frequency of the bearings with rolling bodies is so low that the bearings are liable to become eccentric due to insufficient lubrication or wear. Therefore, the bearings must be periodically replaced with new ones, and cannot stand prolonged continuous use. Thus, the bearings of this type require high machining accuracy and hence entail high costs if they are expected to fulfill their function. Inevitably, moreover, the apparatus must be large-sized.